Attenuated Total Reflection ATR Mode

This attenuation of light is then recorded as absorbance in the spectrum. The light penetrates into the sample at a depth given by the following equation [15]  

As dp is dependent on the angle of incidence, an opportunity exists to change the angle of incidence for depth profiling 

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The sample thickness in the DIT cells (25 pm) is very large in comparison with the usual thickness of samples for infrared transmission studies, and the cell itself is also thick (2.8 mm). Studies in the attenuated total reflectance (ATR) mode do not fit the experiment. For all these reasons, it was by no means certain that infrared studies could in fact be performed using the existing DIT cells. 

Fourier-transformed infrared spectroscopy (FT1R), either in the transmission mode(70), the grazing incidence reflection (GI) mode(7,5) or the attenuated total reflection (ATR) mode(7,2), has been the most widely used experimental tool for the characterization and structure determination of SA monolayers. GI-IR is especially useful in determining the molecular orientation in the film structures because it senses only the vibrational component perpendicular to the substrate surface(7,5). Polarized ATR-IR can also be used to study molecular orientation(7,77). McKeigue and Gula-ri(72) have used ATR-IR to quantitatively study the adsorption of the surfactant Aerosol-OT. 

A Shimadzu UV-3102PC UV-VIS-NIR scanning spectrophotometer was used to record the UV-VIS spectra. Infrared spectra were recorded using a BioRad FTS 6000 spectrometer in the attenuated total reflection (ATR) mode for 200 scans at a resolution of 4 cm The BioRad Merlin software was used to analyze the spectra. 

Figure 2.16. Reflectometry in the attenuated total reflection (ATR) mode.

The main problem in IR measurements in situ is a strong IR absorption by the solvent water. Therefore the measurements in the classical transmission mode are practically excluded (the path length must not exceed 15 tan). Short path lengths are provided by the attenuated total reflection (ATR) mode. The probing light beam undergoes multiple total internal reflection in the ATR element (e.g. a cylindrical rod made of ZnSe, with two cone-sharpened ends) and each reflection... 

The complexity of the FT-IR spectra collected in the Attenuated Total Reflectance (ATR) mode which can include contributions from (a) the adsorbed protein layer or (b) the soluble proteins in the liquid layer adjacent to the ATR surface but within the "depth of penetration" of the evanescent field of the IR beam (this so-called "bulk" effect is especially significant when near-physiological protein concentrations are studied) ... 

The spectrometer may operate in transmission or reflection, but also in attenuated total reflection (ATR) mode, which have been widely used during the last two decades. The transmission mode is very suitable for quantitative analysis, since the main parameters to apply on the Beer-Lambert law are known or easily estimated. The reflection mode is used when polymer is not well dissolved at room temperature, and a film or pellets of the sample is characterized. Such is the case of polyolefins and some engineering polymers like PET. 

Optical Operation Modes Fig. 8 illustrates five types of light incident and collection configurations for the Raman study of an electrode surface. They can be classified into three general kinds of operation modes front incident and collection mode back-scattering mode and the attenuated total reflection (ATR) mode. 

Figure 1(a) shows the Kretschmann configuration [9] for the excitation of plasmon surface polaritons (surface plasmons for short) [10] in the attenuated total reflection (ATR) mode. When a p-polarized laser beam is irradiated at the (internal) incident angle 9t from the prism of a refractive index np above 6c, a strong nonradiative electromagnetic wave, i.e. a surface plasmon is excited at the resonant angle which propagates at the metal /electrolyte interface. 

Siuface functional groups of the membrane were characterized by Fourier transform infrared (FTIR, Varian 1000, Varian Inc., Palo Alto, CA) spectroscopy in attenuated total reflection (ATR) mode. Membrane surface samples were mounted on face of the crystal surface. Spectra were measured in transmittance mode over a wave length of 600-4000 cm at a resolution of 4 cm. ... 

In this chapter, we introduce the principles of the FTIR imaging method and some of the recent applications of FTIR imaging in the study of polymeric materials. This includes an introduction to the general approach of FTIR image acquisition, the transmission and attenuated total reflection (ATR) modes of measurement, the different approaches of measuring liquid and solid samples, the considerations needed to be taken in order to obtain a reliable and accurate imaging measurement and also some of the new opportunities that exist for FTIR imaging. 

Samples representing the storage assemblies were analyzed using micro-Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflectance (ATR) mode. A Nicolet... 

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